Donegal Cancer Flights and Services say they want a resolution by Monday to concerns over the midday Airlink flight from Donegal to Dublin.
The service is widely used by patients travelling for essential medical appointments.
Following discussions with the Department of Transport, the group says officials have confirmed there are no new legal barriers to keeping the previous flight schedule in place.
Department officials remain in negotiations with Emerald Airlines and say they want to resolve the issue as quickly as possible.
Donegal Cancer Flights and Services Manager Mary Coyle says if a satisfactory resolution is not reached, they are prepared to escalate the matter and begin protesting:
